Temperature Guage

[victoryinerie]

1998 5.7 Merc

I did not think my temperature guage was working however I grounded the wire and the guage went to max therefore I assume the guage is fine. I replaced the sender tonight and the guage reallly did not move alot, it took a long time under muffs, it went to 175 for about 5 seconds and than went to 100. I also replace the thermostat. Shouldn't this be running above 100? I did notice the water temperature coming out the outdrive was different temperatures, one was hot (est. 135) and the other was warm (est. 80),

Any suggestions what to check??

 

[NHGuy]

Re: Temperature Guage

Start out by getting a laser non-contact thermometer. They coast about $20 or $30 for the basic home use ones. Use it to observe temps while running, and don't run the engine much over 200 degrees. Also if you get steam from the exhaust shut it down, temps that high ruin stuff in the drive and the exhaust. When you run the engine watch the guage and take temps right off the temperature sending unit. It's also okay to check other areas with the temp gauge, shoot away. Check that the gauge tells real temperatures.
My engine can take what seems like an eternity to warm up. Just run it at 1500 rpms and wait it out. You might be OK on temperature and have a dirty electrical connection to the dash panel.
You do realize there must always be water to the boat while it's running, right?

 

[victoryinerie]

Re: Temperature Guage

Yes the muffs are always on when the engine is running, not sure if it matters but the boat has a Bravo 3 outdrive.

 

[Brentathon]

Re: Temperature Guage

I had an engine circ pump fail (impeller sheared off inside pump), and it made my gauge go to full COLD, yet engine was actually overheating because water was not being pumped through block............was a very tricky problem to fix.
Didn't figure it out, until I removed circ pump, and heard impeller clankin' around inside......

 

[victoryinerie]

Re: Temperature Guage

Just on a side note, not sure if they are related but the tach also seems to jump all over the place at first but than somewhat settles down after the engine runs for a few minutes.

 

[victoryinerie]

Re: Temperature Guage

I hooked up the old sender grounded it too the boat, poored hot water on it and it appears that the guage / sender/ theromostat works fine. For some reason it is running cold.

I called the previous owner to see if he knew anything and he said about 2 years ago he replaced the water pump it was running warm. He had no issues since, he also stated that when he winterized it he removed the thermostat and the white sleeve inside the housing that controls the water flow? Any idea what this is?? Can it be installed incorrectly? I did not see anything when I repleaced the thermostat however I was not looking...

Any suggestions??

 

[Fireman431]

Re: Temperature Guage

Don't forget, it's not like a car that's continually circulating the same warm/hot water in the radiator. A boat is pulling a new supply of cool water every second and that is only going to allow the engine to heat up to a minimal temperature, especially not being under a load. Mine will sit and idle all day at 150 degrees. Once I run the engines under load, they come up to 175 (thankfully not a degree higher).

Cold water from a hose through the muffs and no load...no wonder it takes forever to get to minimal temps.

 

[victoryinerie]

Re: Temperature Guage

Don't forget, it's not like a car that's continually circulating the same warm/hot water in the radiator. A boat is pulling a new supply of cool water every second and that is only going to allow the engine to heat up to a minimal temperature, especially not being under a load. Mine will sit and idle all day at 150 degrees. Once I run the engines under load, they come up to 175 (thankfully not a degree higher).

Cold water from a hose through the muffs and no load...no wonder it takes forever to get to minimal temps.

The issue is before I replaced the sender and thermostat, the guage was doing the same thing in the water under load. Runs about 100 goes up to 175 and than drops down immediatly back down to 100

 

[Brentathon]

Re: Temperature Guage

Fix the white sleeve. Why would he mess with that.
Put everything back to the way it was designed.......there's a purpose for all parts.
Then start your logical troubleshooting process.

 

[Fireman431]

Re: Temperature Guage

It could be from your thermostat opening, but I usually haven't seen temps drop that far. Have you tried a temporary gauge at the water jacket?

 

[Aloysius]

Re: Temperature Guage

If, for some reason, the sender in the intake manifold isn't fully immersed in coolant, it won't read correctly.

 

[victoryinerie]

Re: Temperature Guage

I replaced the white sleeve, all the gaskets, is was missing the one on top of the thermostat. Took the boat out last night, the gauge would stay around 100 occassionly it would go to 120 but than drop back down. I know I somewhat check the gauge by grounding the wire and it pegged but could it some how be off?

If, for some reason, the sender in the intake manifold isn't fully immersed in coolant, it won't read correctly. This was stated eariler, is there a way to check this??

 

[Don S]

Re: Temperature Guage

As was mentioned early in this thread, you have to get an IR Temp gun similar to the one pictured below, and with the engine warmed up take a temperature right at the base of the sending unit and see if the engine is actually running that cool or your temp gauge is off. Then you will at least know where to start troubleshooting.

 

[nola mike]

Re: Temperature Guage

i got one of these. my gauge was off by 30-40'

 

[victoryinerie]

Re: Temperature Guage

Got the IR temperature gun. Under the sender read 155, the water coming out the back was 120. I took a cup of hot water, took a reading and grounded the sender and it was about the same temperature as the guage.

Any thoughts what too look at??

 

[victoryinerie]

Re: Temperature Guage

Got the IR temperature gun. Under the sender read 155, the water coming out the back was 120. I took a cup of hot water, took a reading and grounded the sender and it was about the same temperature as the guage.

Any thoughts what too look at??

Also I replaced the white sleeve in the houseing, is there only one way to install it?? I lined up the grove however could it be 180 out?